Method for manufacturing a film bulk acoustic resonator
A film bulk acoustic resonator, and a method for manufacturing the same. The film bulk acoustic resonator includes a substrate, a protection layer vapor-deposited on the substrate, a membrane vapor-deposited on the protection layer and at a predetermined distance from an upper side of the substrate, and a laminated resonance part vapor-deposited on the membrane. Further, the manufacturing method includes vapor-depositing a membrane on a substrate, forming protection layers on both sides of the membrane, vapor-depositing a laminated resonance part on the membrane, and forming an air gap by removing a part of the substrate disposed between the protection layers. Accordingly, the membrane can be formed in a simple structure and without stress, and the whole manufacturing process is simplified.
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This is a divisional of application Ser. No. 10/929,569 filed Aug. 31, 2004, now U.S. Pat. No. 7,205,702 claiming the benefit of Korean Application No. 2003-69838, filed Oct. 8, 2003, in the Korean Intellectual Property Office; the entire disclosures of the prior applications are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to an acoustic filter used in wireless communication devices, and more particularly, to a film bulk acoustic resonator (hereinafter, referred to as “FBAR”) which implements a high pass filter for passing only a specified high frequency component, and a method for manufacturing the same.
2. Description of the Related Art
As mobile communication devices, such as mobile phones have become popular, a small and light filter for such devices has become increasingly in demand. In the meantime, as a means for implementing the small and light filter, an FBAR has been introduced. The FBAR can be produced in bulk at a very low cost, and manufactured in a very small size. In addition, the FBAR enables a high quality factor value which is a special feature of the filter, and can be used in a micro frequency band. In particular, the FBAR is able to realize even a personal communication system (PCS) band and a digital cordless system (DCS) band.
In general, an FBAR element comprises a laminated resonance part created by a first electrode, a piezoelectric layer and a second electrode vapor-deposited in the above order on a substrate. The FBAR is operated as follows. Electric energy is applied to an electrode, and an electric field which temporally changes is induced in the piezoelectric layer. Then, the electric field causes a bulk acoustic wave in the piezoelectric layer in the same direction as a vibration in the laminated resonance part, and generates the resonance.
The FBAR element includes, as shown in
The Bragg reflector-type FBAR of
On the other hand, the air gap-type FBAR uses an air gap instead of the reflection layer to separate the substrate from the resonance part, and is divided into several types according to the manufacturing method used. Different types of air gap-type FBAR elements are illustrated in
The FBAR element in
The FBAR element in
The FBAR element of
The present invention has been made to overcome the above-mentioned problems in the related art. Accordingly, it is an aspect of the present invention to provide a film bulk acoustic resonator of an improved degree of integration and a simple structure, wherein an air gap is formed by using a part of a substrate oxidized by LOCOS process for an etching stop layer, and etching a part of the other substrate, and the method for manufacturing the same.
In order to achieve the above-described aspects of the present invention, there is provided a film bulk acoustic resonator comprising a substrate, a protection layer vapor-deposited on the substrate, a membrane vapor-deposited on the protection layer and at a predetermined distance from an upper side of the substrate, and a laminated resonance part vapor-deposited on the membrane.
The protection layer is vapor-deposited on both sides of the substrate except for a predetermined part. The laminated resonance part comprises a lower electrode vapor-deposited on the membrane, a piezoelectric layer vapor-deposited on the lower electrode, and an upper electrode vapor-deposited on the piezoelectric layer.
The membrane may be a single layer of nitride, or multiple layers in which a nitride membrane, an oxidized membrane and the nitride membrane are sequentially vapor-deposited.
Meanwhile, a method for manufacturing a film bulk acoustic resonator according to the present invention, comprises the steps of vapor-depositing a membrane on a substrate, forming protection layers on both sides of the membrane, vapor-depositing a laminated resonance part on the membrane, and forming an air gap by removing a part of the substrate disposed between the protection layers.
Here, the protection layer may be formed by a LOCOS process, and the air gap may be formed by dry etching or wet etching.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
As shown in
As shown in
The membrane 150 is vapor-deposited on an upper part of the air gap 100a between the protection layers 110a and 110b which are on the substrate 100. The membrane 150 supports the laminated resonance part 200, and functions as an oxidation stop layer during the LOCOS process. The membrane 150 may be formed of a single layer of nitride as shown in
The laminated resonance part 200 comprises a lower electrode 210, a piezoelectric layer 220, and an upper electrode 230. The lower electrode 210 is vapor-deposited on the membrane 150 and one protection layer 110a, and the piezoelectric layer 220 is vapor-deposited on the lower electrode 210 and the other protection layer 110b. The upper electrode 230 is vapor-deposited on the piezoelectric layer 220. In this example, the lower and the upper electrodes 210 and 230 use a general electric conductor such as a metal, to apply an electric field to the piezoelectric layer 220. For the lower and the upper electrodes 210 and 230, it is preferable to use one of Al, W, Au, Pt, Ni, Ti, Cr, Pd and Mo. The piezoelectric layer 220 causes a piezoelectric effect when being applied with the electric field, and therefore generates an acoustic wave. For the piezoelectric material, AlN, ZnO, or other material can be used. The acoustic wave generated at the piezoelectric layer 220 is reflected by the air gap 100a, and the resonance effect is enlarged.
The laminated resonance part 200 comprises a lower electrode 210, a piezoelectric layer 220, and an upper electrode 230. The lower electrode 210 is vapor-deposited on the membrane 150 and one of the protection layer 110a, and the piezoelectric layer 220 is vapor-deposited on the lower electrode 210 and the other protection layer 110b. The upper electrode 230 is vapor-deposited on the piezoelectric layer 220. In this example, the lower and the upper electrodes 210 and 230 use a general electric conductor such as a metal, to apply an electric field to the piezoelectric layer 220. For the lower and the upper electrodes 210 and 230, it is preferable to use one of Al, W, Au, Pt, Ni, Ti, Cr, Pd and Mo. The piezoelectric layer 220 causes a piezoelectric effect when being applied with the electric field, and therefore generates an acoustic wave. For the piezoelectric material, AlN, ZnO, or other material can be used. The acoustic wave generated at the piezoelectric layer 220 is reflected by the air gap 100a, and the resonance effect is enlarged.
Hereinafter, a method for manufacturing the FBAR element according to an embodiment of the present invention will be described with reference to
After the air gap 100a is formed, the FBAR having the structure in
Although the present invention has been described above with reference to the FBAR element, it is not for purpose of limitation, and therefore, other various semiconductor elements using a specific layer vapor-deposited on the silicon substrate can be applied.
As described above, according to the present invention, since the element is formed on a surface of the substrate 100, the element occupies a minimum area, and therefore, the element has an improved degree of integration. Furthermore, using the LOCOS process, the membrane 150 can be formed in a simple structure and without stress.
In addition, since a flattening process as in the prior art is omitted, the whole manufacturing process can be simplified. Furthermore, the LOCOS process is compatible with a CMOS process.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims
1. A method for manufacturing a film bulk acoustic resonator comprising:
- vapor-depositing a membrane on a substrate;
- forming protection layers on the substrate which abut two sides of the membrane;
- vapor-depositing a laminated resonance part on the membrane; and
- forming an air gap by removing a part of the substrate disposed between the protection layers.
2. The manufacturing method of claim 1, wherein the protection layers are formed by a LOCOS process.
3. The manufacturing method of claim 1, wherein the step of vapor-depositing a laminated resonance part comprises:
- vapor-depositing a lower electrode on the membrane;
- vapor-depositing a piezoelectric layer on the lower electrode; and
- vapor-depositing an upper electrode on the piezoelectric layer.
4. The manufacturing method of claim 1, wherein the air gap is formed by dry etching.
5. The manufacturing method of claim 1, wherein the air gap is formed by wet etching.
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Type: Grant
Filed: Mar 19, 2007
Date of Patent: Sep 14, 2010
Patent Publication Number: 20070157442
Assignee: Samsung Electronics Co., Ltd. (Suwon-si)
Inventors: Byeoung-ju Ha (Yongin-si), Yun-kwon Park (Dongducheon-si), In-sang Song (Seoul), Il-jong Song (Suwon-si), Jong-seok Kim (Gyeonggi-do), Duck-hwan Kim (Seoul), Jun-sik Hwang (Ohsan-si)
Primary Examiner: Derris H Banks
Assistant Examiner: Tai Nguyen
Attorney: Sughrue Mion, PLLC
Application Number: 11/687,734
International Classification: H01L 41/22 (20060101); H01L 41/00 (20060101);